The present invention relates to SIP based communication and data systems. The abbreviations used herein shall have the following meanings:
CS: Circuit Switched
CSCF: Call Session Control Function
DevID: Device Identifier
ESN: Electronic Serial Number
GRUU: Globally Routable User Agent (UA) URIs
HSS: Home Subscriber Server
I-CSCF: Interrogating CSCF
ICS: IMS Centralized Services
ID: Identifier
IMEI: International Mobile Equipment Identity
IMEISV: IMEI Software Version
IMS: IP Multimedia Subsystem
IP: Internet Protocol
MEID: Mobile Equipment Identifier
MSC: Mobile Switching Center
NAI: Network Access Identifier
NSS: Name Space Specific string
P-CSCF: Proxy CSCF
PS: Packet Switched
S-CSCF: Serving CSCF
SCC AS: Service Centralization and Continuity Application Server
SIP: Session Initiation Protocol
SNR: Serial Number
TAC: Type Allocation Code
UA: User Agent
UE: User Equipment
URI: Uniform Resource Identifiers
URN: Uniform Resource Name
UUID: Universally Unique Identifier
In SIP-based systems, such as IMS, it would be advantageous to be able to target a request to a specific device, such as a mobile device, fixed line device, or an instance of a software based client. A software based client is not directly tied to a specific physical device and may execute on top of any suitable platform such as a personal computer or advanced mobile device. For example, when transferring a call, one may wish to target a specific device such as a user's mobile device.
In order to achieve this objective, a Globally Routable User Agent (UA) URN (GRUU) is assigned to the mobile device by the registrar (which is the S-CSCF in an IMS system). In order to properly assign the GRUU, the registrar uses an Instance ID that is provided by the mobile device during registration.
Current specifications assume that the device being targeted with the GRUU will always be the one that is performing the registration. However, with the introduction of IMS Centralized Services (ICS), it is possible that the network will register (in IMS) on behalf of the device when the device is using circuit-switched (CS) access. In the case of ICS, the MSC Server is the network entity that registers on behalf of the CS subscriber.
Since an ICS device may also be able to register directly (in IMS) when it is using packet-switched (PS) access, it is desirable that the Instance ID that is used by the network be identical to the Instance ID that is used by the device when performing registration. This will ensure that the same GRUU is assigned to the device.
The current IMS specifications (such as 24.229) do not provide any specific guidance on how either the device or the network are to create the Instance ID. The only guidance that is provided is that the Instance ID must match the format described in the IETF Outbound draft. Therefore, the current specifications do not ensure that the Instance ID used by the network will match the Instance ID used by the device.
Additionally, the current IMS specifications do not provide any guidance on how the registrar shall generate the GRUU from the Instance ID. This can lead to the generation of different GRUUs depending on which S-CSCF is assigned during registration, if different S-CSCF vendors choose to generate the GRUU in different ways.
A possible Instance ID would be to use an already existing equipment identity from the terminal, such as the IMEI, as the Instance ID. In the case that the S-CSCF were to simply use the Instance ID unchanged as the GRUU, as provided as an example in draft-ieff-sip-gruu-15, then this would expose the DevID to other users during session establishment. This could be considered a privacy violation and could be used to clone the equipment. Therefore, directly using an existing device identity such as the IMEI is not recommended from a privacy and security point of view.
It would be advantageous to have a method and apparatus for an instance ID based on a unique device identifier that overcomes the disadvantages of the prior art. The present invention provides such a method and apparatus.